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Thread: No silk thread method?

  1. #1

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    No silk thread method?

    Saw this mentioned on another thread (no pun).

    I have been assembling small Continental engines with no thread for about a half century - not lots, but enough to keep me flying. I originally used Rolls Royce Hylomar, which is no longer a good choice (Loctite makes an orange equivalent). I have never had any problems.

    Local shop is getting ready to assemble a C-90. I would recommend no thread based on my own experience, but that is a lousy way to back up such a recommendation.

    Are major shops moving away from the silk thread method of case assembly? Or am I making a mistake?

  2. #2
    Steve Pierce's Avatar
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    I would reference TCM SIL99-2C or latest revision. I haven't seen a published procedure on a Continental that doesn't use silk thread, Lycoming has a published method.
    Steve Pierce

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  3. #3
    Steve Pierce's Avatar
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    Not sure if this is the latest revision but food for thought.
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    Steve Pierce

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    DUSTERMAN's Avatar
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    How about Anaerobic gasket maker. I've heard that the car manufactures are using it on the new engines. I've used it a bit on cars and tractors. Very easy to use. It doesn't start to seal until the parts are put together (no air).

  5. #5
    Steve Pierce's Avatar
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    Alternate method from Lycoming is to use RTV-102 or Loctite 515. I have used them on Lycomings without issue. Also had LyCon o'ring the crank case which is really nice.https://www.lycoming.com/sites/defau...20Sealants.pdf
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    wireweinie's Avatar
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    I know most are tired of hearing it, but how about doing it the way the manual says? If it says sealant, use THAT sealant. If it says use silk thread, use silk thread. If it says no sealant, don't put it on.

    Crankcase halves are critical in that if damaged, you'll have no engine. But it's also critical in that if assembled and found to be leaking (or assembled incorrectly) you'll need to remove the engine from the aircraft and then disassemble it completely to fix.

    Just follow the manual.

    Web
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  7. #7

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    Quote Originally Posted by DUSTERMAN View Post
    How about Anaerobic gasket maker. I've heard that the car manufactures are using it on the new engines. I've used it a bit on cars and tractors. Very easy to use. It doesn't start to seal until the parts are put together (no air).
    Might be fine with an EX engine but nothing you want to use in a Certified build.
    One thing Lycoming noted about non approved sealants is people select a sealant like you mention, but that sealant was never approved to be used between critical machined surfaces. Most of those sealants are designed for timing case covers and oil sumps essentially engineered as a gasket replacement.
    In those applications, even after torquing the fasteners the sealant has a measurable thickness. It then is prone to a slow creep out of the joint.
    Two issues here, the slight thickness imposed by the sealant reduces bearing shell crush right from assembly.
    Second the chance of slow creeping my result in loss of torque on through fasteners. Nether is a good thing.

    There are sealants that could be considered safe such as those used on case halves of motorcycle engines as well as outboard motors. But I would truly not go there on a Certified engine and make sure you truly understand the sealant's properties.

    The recommended and approved Locktite 515 is derived from that family of sealants.
    Likes mike mcs repair, Jonnyo liked this post

  8. #8

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    Hylomar and silk thread work well. FWIW, my brand new Lycoming has silk thread.

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    Quote Originally Posted by DUSTERMAN View Post
    How about Anaerobic gasket maker. I've heard that the car manufactures are using it on the new engines. I've used it a bit on cars and tractors. Very easy to use. It doesn't start to seal until the parts are put together (no air).
    Thats what I used on the last 2, one 14 years ago and over 1200 hrs. No leaks anywhere

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  10. #10
    Steve Pierce's Avatar
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    Ask Frank Sparandeo "Miss Pearl" about using some alternative sealant and what happened to the engine on his Pacer.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  11. #11

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    Silk thread is a great product for the application. I don't understand why anyone would resist using what's worked for 80 years. Sealants are better, sure, so why not use both?

  12. #12
    cubdriver2's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Ask Frank Sparandeo "Miss Pearl" about using some alternative sealant and what happened to the engine on his Pacer.
    Why would anyone listen to that idiot?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  13. #13
    Steve Pierce's Avatar
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    I'd pee on his tie down ropes myself. Legend in his own mind.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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  14. #14
    cubdriver2's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I'd pee on his tie down ropes myself. Legend in his own mind.
    Me too or been there done that

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  15. #15
    BC12D-4-85's Avatar
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    You guys are ruff. I've had wolves pee on my tie down ropes but never a two legger that lived to talk about it.

    Gary
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  16. #16

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    Quote Originally Posted by Steve Pierce View Post
    I'd pee on his tie down ropes myself. Legend in his own mind.
    Had a roommate in college that would borrow money then conveniently forget to pay you back. If asked about it he would shrug his shoulders and tell you next week. Instead of getting mad, we’d move his bed, pee on the carpet then move the bed back. This happened “several” times over a year. He never could figure out where the smell was coming from. This turned out to be the ultimate in anger relief.
    ......Oh, by the way, his room was the only one that didn’t have a window that would open

  17. #17

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    Apparently there's a competition for top idiot. It used to be an interesting topic.

  18. #18

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    Quote Originally Posted by stewartb View Post
    Apparently there's a competition for top idiot. It used to be an interesting topic.
    No one said you had to read every post. If all you were wanting was technical information you should have stopped at the sealant PDFs. Sorry about the kids playing on your yard. Build a taller fence or buy a bigger dog.
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  19. #19

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    We have a new leader.
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  20. #20

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    springs just around the corner, hold on.
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  21. #21

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    Quote Originally Posted by bob turner View Post
    Saw this mentioned on another thread (no pun).

    I have been assembling small Continental engines with no thread for about a half century - not lots, but enough to keep me flying. I originally used Rolls Royce Hylomar, which is no longer a good choice (Loctite makes an orange equivalent). I have never had any problems.

    Local shop is getting ready to assemble a C-90. I would recommend no thread based on my own experience, but that is a lousy way to back up such a recommendation.

    Are major shops moving away from the silk thread method of case assembly? Or am I making a mistake?
    Why is Hylomar no longer a good choice?
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  22. #22
    Steve Pierce's Avatar
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    The topic tripped a trigger Stewart, Frank had his engine start coming apart from using silicone on the cylinder bases, he is a DER/A&P/IA and self proclaimed expert but the coup de grace was when as the president of the Short Wing Piper he sued SJ and I over using the name Short Wing on our website. These threads are kinda like bullshit sessions in person you just don't get to hear the laughter and the different accents.
    Steve Pierce

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    Will Rogers

  23. #23
    txpacer's Avatar
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    You should start a Frank thread and post his adventure adjusting the ailerons on his Pacer
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  24. #24
    Steve Pierce's Avatar
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    Quote Originally Posted by txpacer View Post
    You should start a Frank thread and post his adventure adjusting the ailerons on his Pacer
    In flight and he disconnected them and the cable fell under the floor?
    Steve Pierce

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  25. #25
    txpacer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    In flight and he disconnected them and the cable fell under the floor?
    Just for the sake of levelling the yokes

  26. #26
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    Quote Originally Posted by bob turner View Post
    ….I have been assembling small Continental engines with no thread for about a half century - not lots, but enough to keep me flying. I originally used Rolls Royce Hylomar, which is no longer a good choice (Loctite makes an orange equivalent). ….
    Please elaborate on the hylomar comment.
    Cessna Skywagon-- accept no substitute!

  27. #27

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    Okay. My first tube was in 1966. $35. That was almost half of my monthly paycheck (military).

    Loctite started making it about 20 years ago - $2.50/tube.

    Two or so years ago I tried to buy another tube (stuff lasts a long time). $11 bucks, but not the same stuff, and not Loctite. It came out of the tube like cottage cheese.

    So I contacted Loctite. Had a nice phone conversation with an engineer. They had some kind of licensing problem (odd, I guess, because patents run out after a max of 20 years, so it may be a “branding” problem).

    i suspect they kept the formula, and changed the name (I can get it) and the color (blue to orange).

    In any case, my understanding was that Rolls Royce had approval to do away with the silk thread. Been a very long time, and I cannot prove it. I would love to know how the silk thread prevents fretting.

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    Correction - not Loctite. Permatex “Permashield” 85420. And it was via e-mail:

    We sold Hylomar thru Permatex back in the 90’s but they pulled the plug from us. We have an item called Permashield which is a substitute but has not been tested or approved for aviation use. I do know that Hylomar is still around because I saw them at an engine expo in Chicago in 2017. They seem to have even more products than before.

  29. #29

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    This is the outfit from which I bought the tube of cottage cheese. Perhaps I failed to research - they apparently have lots of different types. I suspect, but am not sure, that the Aero grade is the same as the old Rolls Royce stuff. The orange Permatex spreads like the original RR, but I have not assembled and flown an engine with it.

    http://hylomar.com/hylomar-product-r...#aerogradepl32

  30. #30
    BC12D-4-85's Avatar
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    Notice the varying torque requirements after assembly: http://hylomar.com/warrick/wp-conten...version-11.pdf

    Gary

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    Had o-235 that was assembled with star washers under cylinder hold down nuts.

  32. #32
    wireweinie's Avatar
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    Quote Originally Posted by bob turner View Post
    I would love to know how the silk thread prevents fretting.
    It doesn't. It forms a sort of gasket between the case halves. Mechanical force and a precise fit prevent fretting.

    Web
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  33. #33
    n40ff's Avatar
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    I used hylomar & silk thread recently. New tube looked like cottage cheese but was ok after I mixed it up and threw the first little bit away. My take is that the hylomar never dries and does not resist torque. It serves to hold the silk thread while you assemble the case halves. The silk thread is to prevent oil leaks, nothing else. Fretting seems relative to power. Lycoming progressively needed to dowel cases and bearings as power went up.... My read from the Lycoming manual and SB's on "no thread" was that it worked ok with approved sealants as long as final assembly and torque was done right away. With thread and proper non hardening sealant, you can assemble cases and then install cylinders later.

    I found much seemingly good info on motorcycles and boat motors that would seem to offer good advice but decided that following factory dirrections was best. While my engines are experimental, my life isn't.

    I've gone back and checked torque and have NEVER been able to move a nut at max torque. I believe that if I did it would mean I didn't get it right the first time. Of coarse I only have low compression O290 and O320 engines. With higher PSI units YMMV for sure.

    BTW, I have seen several lycoming O235 and O290 G/D engines with star lock washers under the cylinder base nuts. One is my own O290G that was assembled by an IA and has several 100 hours. I couldn't move any nuts at spec. torque. I suspect that if properly lubed the star washers will not prevent "adequate" torque from being applied and might not hurt, at least not on those low compression engines. But why in the world use them?

    OTOH I had a first run O235C1 with 1500TT that was moderately fretted when opened at an aviation school. I had the logs and it was never opened. Makes you wonder?

    Bottom line for me anyway is that there is an overload of infomation out there including this forum (which I feel is excellent). I decided to do what Lycoming said to do. My choice was a approved non hardening sealant(hylomar) and silk thread or one of the two approved "no thread" sealants. I chose the former since I wasn't planing on applying final torque for several days.

    I've also seem to many cylinders that had obviously too much paint on the cylinder base flanges. I do not want to believe a certified shop painted them. I also took apart a very old high time converted O290G with paint under the cylinder flanges that seem none the worse. In retrospect, I've owned several aircraft over the years mostly E-AB but a couple certified. My conclusion is that the only way to KNOW that your engine was assembled correctly is to have done it yourself...and then hope YOU didn't have a senior moment...or two...or more...

    Oh well,

    Jack
    Last edited by n40ff; 02-29-2020 at 11:40 AM.

  34. #34
    DUSTERMAN's Avatar
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    Loctite 515 is anaerobic sealant

  35. #35
    DUSTERMAN's Avatar
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    Quote Originally Posted by CharlieN View Post
    Might be fine with an EX engine but nothing you want to use in a Certified build.
    One thing Lycoming noted about non approved sealants is people select a sealant like you mention, but that sealant was never approved to be used between critical machined surfaces. Most of those sealants are designed for timing case covers and oil sumps essentially engineered as a gasket replacement.
    In those applications, even after torquing the fasteners the sealant has a measurable thickness. It then is prone to a slow creep out of the joint.
    Two issues here, the slight thickness imposed by the sealant reduces bearing shell crush right from assembly.
    Second the chance of slow creeping my result in loss of torque on through fasteners. Nether is a good thing.

    There are sealants that could be considered safe such as those used on case halves of motorcycle engines as well as outboard motors. But I would truly not go there on a Certified engine and make sure you truly understand the sealant's properties.

    The recommended and approved Locktite 515 is derived from that family of sealants.

    Loctite 515 is anaerobic

  36. #36
    high time cub's Avatar
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    Quote Originally Posted by CharlieN View Post
    the slight thickness imposed by the sealant reduces bearing shell crush right from assembly.
    Catching up on some old posts….

    Slight thickness... HA!


    Many moons ago under the shade of a tree, a humble A-65 was overhauled, hung on a Cub, fired-up, found to have low oil pressure, removed from said Cub and subsequently sold. A good friend of mine bought the pig-in-a-poke engine for a song. He assumed that the low oil pressure was probably due to a worn accessory case having been re-installed but upon disassembly, the oil pump area and gears were perfect. Hmmm…

    Further tear-down found the culprit: a large strand of rib-stitch cord had been substituted for silk. After the offending cord was removed and the case halves properly joined, the A-65’s oil pressure ran silky smooth.

    HT
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